implement login form
LOGIN_REQUIRED ALL THE THINGS
add logout link (not a very nice one, but it'll do)
Lock down verdantusers app to users with can_change_user permission only
Record the user in page_revisions
Merge branch 'develop' into users
Merge branch 'develop' into users

Conflicts:
	django-verdant/verdantadmin/views/pages.py
Merge branch 'develop' into users

Conflicts:
	django-verdant/verdantadmin/views/chooser.py
temporarily remove 'remember me' / 'forgotten password' from login page
Merge branch 'users' into develop